Hi phillay, tris amp will work beso with higo impedance headphones ir hard to drive headphones with lo sensitivity like your AKG. Terrible with hifi 400's. Other wise, with good tube tolling and DAC matching, this amp can and will sound awesome!!! I use AKG 7xx, Beyerdynamics 770 & 880.

Check then the the specs of the Quad Pa One, it is transformer coupled . The difference between Senn HD700 and HE400 on the one side (muddy, dark, slow, veiled) of the same amp compared to the very picky GS1000 (sounded just excellent) was immense, and extremely hearable.